The present invention relates to a photoelectric conversion element or a solar battery which makes use of an organic photoconductive material. The photoelectric conversion element of the present invention is suitable for use in, for example, sensors such as light sensors, image sensors and so forth.
Hitherto, various proposals and attempts have been made in regard to production of photoelectric conversion elements from inorganic semiconductor materials with an aim to obtain a photoelectric conversion element which is inexpensive but yet capable of performing photoelectric conversion with a high degree of efficiency.
For instance, it has been attempted to put various materials such as single-crystalline Si, polycrystalline Si, CdS, CdTe, GaAs and amorphous Si into practical use as materials of photoelectric conversion elements. These substances, however, cannot well meet the demand for inexpensive photoelectric conversion elements.
In order to obviate these shortcomings, in recent years, proposals have been made in regard to techniques for producing photoelectric conversion elements with organic semiconductor layers.
Examples of such semiconductor layers are:
(a) Spinner-applied merocyanine dye layer (disclosed in Japanese Pat. Application Laying Open Nos. 51-122389 and 53-131782, as well as in JOURNAL OF APPLIED PHYSICS 49, 5982 (1978) by A. K. Ghosh)
(b) Laminate of an electron donor layer such as of phthalocyanine or ovalen and an electron acceptor layer such as of a pyrylium-type dye (disclosed in Japanese Pat. Application Laying Open Nos. 54-27787 and 60-201672, as well as in JOURNAL OF APPLIED PHYSICS 52, 5218 (1981) by B. R. Loutfy)
(c) A eutectic complex layer generated from a pyrylium-type dye and polycarbonate (disclosed in Japanese Pat. Application Laying Open No. 54-27387)
(d) A layer composed of non-metal phthalocyanine dispersed in a binder (disclosed in Japanese Pat. Application Laying Open No. 55-9497)
(e) A laminate of an n-type silicon layer and a p-doped polyacetylene thin film (disclosed in Japanese Pat. Application Laying Open Nos. 55-130182 and 55-138879, as well as in JOURNAL OF APPLIED PHYSICS 38, 555 (1981) by B. R. Weinberger)
(f) Vacuum-evaporated merocyanine dye layer (disclosed in Japanese Pat. Application Laying Open No. 56-35477)
In the use of these organic semiconductor materials, one of such semiconductor materials alone or together with a suitable binder is dissolved or dispersed in a medium and the thus formed solution or dispersion is applied on a substrate. Alternatively, one of these semiconductor materials is vacuum-evaporated at a low temperature so as to form a deposition layer on the substrate and another conductive layer is formed on the deposition layer. Although these methods provide inexpensive photoelectric conversion elements of comparatively large areas, such elements are still unsatisfactory in that the conversion efficiency is impractically low.